These
findings warn that procreation
in space may be fraught with peril. However, further research
could help
unlock ways to combat the negative effects that weightlessness has on
people of
all ages.

The
microgravity that astronauts experience orbiting Earth on the
space shuttle or International Space Station can ravage
their bodies on lengthy missions, atrophying muscles,
weakening bones and
causing irregular heartbeats. To advance longer and farther into space,
researchers want to curtail these risks.

By
analyzing the effects of weightlessness on the cellular level,
scientists in Australia now believe they have pinpointed the roots of
its
harmful consequences. Microgravity apparently tampers with stem cells,
which
all other cells originate from. Stem cells normally act as a repair
system for
the body by replenishing its tissues.

By
uncovering the origins of these problems, the investigators now
hope to design remedies that can truly help fix them.

"Our
research is headed toward creating countermeasures that
can be utilized by biomedical
intervention for astronauts," said researcher Helder Marcal,
a tissue
engineer at the University of New South Wales in Australia.

In
their experiments, researchers employed human embryonic stem
cells, which possess the extraordinary ability to become any other
cell. To
simulate microgravity on Earth, the scientists used a NASA-designed
machine
which kept the cells nourished with oxygen and nutrients while
constantly
spinning to keep the cells in a state of freefall for 28 days.

After
this experiment, the cells showed vast differences on the
molecular level, with 64 percent of their proteins differing from those
grown
under normal gravity. Specifically, these microgravity-exposed cells
generated
more proteins that degrade bone and fewer proteins with antioxidant
effects.
Antioxidants protect against reactive oxidants that can damage DNA.

Microgravity
also influenced levels of a broad range of other
proteins. These include those involved in cell division, the immune
system, the
muscle and skeletal systems, calcium levels within cells, and cell
motility.

"The
simulated microgravity experiments we are investigating don?t seem to
suggest a
very positive outcome," Marcal said.

Some
of the detrimental risks that microgravity may have on an embryo
include
inhibited bone maturation, heart and blood vessel alterations, delayed
neural
growth, and altered muscle tissue maturation, Marcal speculated.

"The
effect that microgravity may have on a growing embryo or fetus would be
similar
to an adult body ? however, much more detrimental," Marcal said. "The
adult body can adapt to some microgravity space environments ? however,
what
remains totally unknown is if an embryo can adapt to such an
environment
too."

The
researchers now aim to decipher why exactly microgravity is having
these
molecular effects. "What
we are almost certain of is that the human body depends
and relies on gravity for some mechanical or circulatory
feedback,"
Marcal said.

Mechanical
feedback is needed by bone, while circulatory feedback
is needed by blood vessels. "Vessel walls become weak and our
circulation
and immune system becomes compromised," Marcal explained.

The
researchers are now testing other cell types to analyze the
effects of simulated microgravity on those. In addition, they are
working on
tissues grown from cells that actually flew on one of the recent space
shuttle
missions.

"Thus
we are hoping to combine and complement our
ground-based experiments with those in real space conditions," said
researcher Brendan Burns, a biologist at the University of New South
Wales.

"Human
procreation in space is inevitable, I believe,"
Marcal said.

When
it comes to whether or not medical interventions might protect embryos
and
fetuses from the hazards of microgravity, "therapeutic and
pharmaceutical
intervention may not be the optimum outcome," Marcal said. "Humans
may have to consider that in the not so distant future, genetic
engineering our
bodies may the way forward if we are to explore planets in our solar
system.
However, this raises other ethical and moral issues."

The
scientists detailed their findings at the Astrobiology Science
Conference 2010 in Texas in April.

Charles Q. Choi is a contributing writer for Space.com and Live Science. He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica.